day18/2 bash

day18/Makefile

@@ -8,7 +8,7 @@ export PATH := .:$(PATH)
 
 .PHONY: clean all compile deploy ex1 ex2
 
-all: ex1
+all: ex1 ex2
 
 output:
 	@$(MAKE) --no-print-directory all 2>&1 > OUTPUT

day18/OUTPUT

@@ -1,4 +1,8 @@
 ex1.bash : res=650217205854
-	time: 0:01.73 real, 1.73 user, 0.00 sys
+	time: 0:01.76 real, 1.74 user, 0.01 sys
-	context-switch:	6+1, page-faults: 0+189
+	context-switch:	5+1, page-faults: 0+188
+
+ex2.bash : res=20394514442037
+	time: 0:01.54 real, 1.53 user, 0.01 sys
+	context-switch:	42+1, page-faults: 0+196
 

day18/README

@@ -36,8 +36,6 @@ Here are a few more examples:
 Before you can help with the homework, you need to understand it yourself. Evaluate the expression on each line of the homework; what is the sum of the resulting values?
 
 Your puzzle answer was 650217205854.
-
-The first half of this puzzle is complete! It provides one gold star: *
 --- Part Two ---
 
 You manage to answer the child's questions and they finish part 1 of their homework, but get stuck when they reach the next section: advanced math.
@@ -63,8 +61,6 @@ Here are the other examples from above:
 
 What do you get if you add up the results of evaluating the homework problems using these new rules?
 
-Answer:
+Your puzzle answer was 20394514442037.
 
-Although it hasn't changed, you can still get your puzzle input.
+Both parts of this puzzle are complete! They provide two gold stars: **
-
-You can also [Share] this puzzle.

day18/ex2.bash

@@ -0,0 +1,168 @@
+#!/bin/bash
+#
+# ex2.bash: Advent2020 game, day 18/game 2.
+
+CMD=${0##*/}
+set -o noglob
+
+# shellcheck disable=2034
+declare -a STACK=()
+declare -a LINE=()
+
+function enqueue() {
+    local -n stack="$1"
+    local var="$2"
+    stack=("$var" "${stack[@]}")
+}
+function dequeue() {
+    # shellcheck disable=2178
+    local -n stack="$1"
+    local -n var="$2"
+    local last=$((${#stack[@]} - 1))
+    var=${stack[$last]}
+    unset 'stack[$last]'
+    stack=( "${stack[@]}" )                       # pack
+}
+function getqueue() {
+    # shellcheck disable=2178
+    local -n stack="$1"
+    local -n var="$2"
+    local pos="$3"
+
+    var=${stack[$pos]}
+    unset 'stack[$pos]'
+    #stack=( "${stack[@]}" )                       # DO NOT pack !
+}
+function setqueue() {
+    local -n stack="$1"
+    local val="$2"
+    local pos="$3"
+
+    stack[$pos]="$val"
+}
+function print_stack() {
+    # shellcheck disable=2178
+    local -n stack="$1"
+    local k
+    printf "stack [%s:%d]: " "$1" "${#stack[@]}"
+    for k in "${!stack[@]}"; do
+        printf "%s:%s " "$k" "${stack[$k]}"
+    done
+    printf "\n"
+}
+
+function eval_plus() {
+    local -n lvalop="$1" loptop="$2"
+    local -i v v1 v2 pos last="${#loptop[@]}"
+
+    for ((pos=0; pos<last; ++pos)); do
+        if [[ "${loptop[$pos]}" == '+' ]]; then
+            getqueue lvalop v1 "$pos"
+            getqueue lvalop v2 "$((pos+1))"
+            getqueue loptop op "$pos"
+            # shellcheck disable=SC1102
+            v=$((v1 + v2))
+            setqueue lvalop "$v" $((pos+1))
+        fi
+    done
+    lvalop=("${lvalop[@]}")                     # pack arrays
+    loptop=("${loptop[@]}")
+}
+
+function eval_op() {
+    # shellcheck disable=2034,2178
+    local -n lvalop="$1" loptop="$2"
+    # shellcheck disable=2034
+    local v v1 v2 op res=-1
+    while ((${#lvalop[@]} > 1)); do
+        dequeue lvalop v1
+        dequeue lvalop v2
+        dequeue loptop op
+        # shellcheck disable=SC1102
+        v=$((v1 "$op" v2))
+        enqueue lvalop "$v"
+        ((res++))
+    done
+    return "$res"
+}
+
+function find_paren() {
+    local -n expr_="$1"
+    local -n var_="$2"
+    local -i i
+    local k val
+    var_=-1
+    for k in "${!expr_[@]}"; do
+        val=${expr_[$k]}
+        [[ $val == '(' ]] && i="$k"
+        if [[ $val == ')' ]]; then
+            # shellcheck disable=SC2034
+            var_="$i"
+            break
+        fi
+    done
+}
+
+function eval_expr() {
+    local -i cur="$2" val len=${#LINE[@]}
+    local op
+    # shellcheck disable=SC2034
+    local -a lstack=() lop=() LINE_=()
+
+    while ((cur < len)); do
+        symbol=${LINE[$cur]}
+        case "$symbol" in
+            [0-9]*)
+                enqueue lstack "${LINE[$cur]}"
+                unset 'LINE[$cur]'
+                ;;
+            \))
+                break
+                ;;
+            [\+\*]*)
+                enqueue lop "${LINE[$cur]}"
+                unset 'LINE[$cur]'
+                ;;
+            *)
+                exit 1
+                ;;
+        esac
+        ((cur++))
+    done
+    eval_plus lstack lop
+    eval_op lstack lop
+
+    dequeue lstack val
+    LINE[$cur]="$val"
+    LINE=("${LINE[@]}")                   # pack
+}
+
+declare -i res=0 paren=0
+
+while read -r line; do
+    # cleanup input line, force split around operators and parens
+    line=${line//\*/ * }
+    line=${line//+/ + }
+    line=${line//-/ - }
+    line=${line//\// \/ }
+    line=${line//\(/ \( }
+    line=${line//\)/ \) }
+    read -ra LINE <<< "$line"
+    paren=0
+    while ((${#LINE[@]} > 1 && paren >= 0)); do
+        find_paren LINE paren
+        if (( paren >= 0 )); then
+            unset 'LINE[$paren]'
+            LINE=("${LINE[@]}")                     # pack
+            eval_expr STACK "$paren"
+        fi
+    done
+    if ((${#LINE[@]} > 1)); then
+        eval_expr STACK 0
+    fi
+    ((res+=LINE[0]))
+done
+
+printf "%s : res=%d\n" "$CMD" "$res"
+
+exit 0